Wireless power transmitter and wireless power transmission method

ABSTRACT

A wireless power transmitter is disclosed. The wireless power transmitter, which is capable of charging a plurality of wireless power receivers, includes: a plurality of coil cells; a main half-bridge inverter to which a main pulse signal is applied; a plurality of sub half-bridge inverters to which a first sub pulse signal or second sub pulse signal is applied; a current sensor that monitors the current through the coil cells; and a communications and control unit that controls the pulse signals applied to the main half-bridge inverter and sub half-bridge inverters and that communicates with the wireless power receivers, wherein the sub half-bridge inverters may be respectively connected to the coil cells.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Phase of PCT International ApplicationNo. PCT/KR2015/003594, filed on Apr. 10, 2015, which claims priorityunder 35 U.S.C. 119(e) to U.S. Provisional Application Nos. 61/978,592,filed on Apr. 11, 2014 and 61/979,867, filed on Apr. 15, 2014, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

TECHNICAL FIELD

The present invention relates to a wireless power transmitter and awireless power transmission method, and more particularly, to a wirelesspower transmitter which can charge one or multiple wireless powerreceivers and a wireless power transmission method.

BACKGROUND ART

Contactless wireless charging is an energy transfer method thatelectromagnetically transfers energy without wires, as opposed to theexisting method that transmits energy through wires and uses it as apower source for electronics. Contactless wireless transmission methodsinclude electromagnetic induction and resonant coupling. Electromagneticinduction is a power transfer method in which a power transmission partproduces a magnetic field in a power transmitting coil (primary coil),and in which a receiving coil (secondary coil) is placed in a positionwhere a current can be induced. Resonant coupling is the transmission ofenergy that uses resonance between a primary coil and a secondary coil,in which resonant mode energy is coupled between the coils as theprimary coil and the secondary coil resonate at the same frequency.

DISCLOSURE Technical Problem

Recently, electromagnetic inductive wireless chargers for mobiledevices—that is, wireless power transmitters—are being developed.Notably, the WPC (Wireless Power Consortium) is working toward thestandardization of wireless power transmission technology to enableinteroperability across wireless power transmitters.

The released WPC standard is a low-power specification designed forcharging low-power mobile devices. However, along with thediversification of mobile devices and the need for higher chargingefficiency, there is growing demand for higher-power charging. Moreover,as wireless charging technology is rapidly becoming commerciallyavailable, there is also a need for methods that allow multiple mobiledevices to be charged simultaneously for user convenience.

Technical Solution

The present invention has been made in an effort to solve theabove-described technical problems, and one embodiment of the presentinvention provides a wireless power transmitter which is capable ofcharging a plurality of wireless power receivers, the wireless powertransmitter including: a plurality of coil cells; a main half-bridgeinverter to which a main pulse signal is applied; a plurality of subhalf-bridge inverters to which a first sub pulse signal or second subpulse signal is applied; a current sensor that monitors the current ofthe coil cells; and a communications and control unit that controls thepulse signals applied to the main half-bridge inverter and subhalf-bridge inverters and that communicates with the wireless powerreceivers, wherein the sub half-bridge inverters may be respectivelyconnected to the coil cells, and the first sub pulse signal may be aphase-inverted version of the main pulse signal and the second sub pulsesignal may be a phase-controlled version of the main pulse signal.

In the wireless power transmitter according to the embodiment of thepresent invention, the communications and control unit may apply thesecond sub pulse signal to at least one of the sub half-bridge invertersto discover a power receiver.

In the wireless power transmitter according to the embodiment of thepresent invention, at least one of the coil cells receives a responsefrom a power receiver, the communications and control unit may performpower transmission by applying the first sub pulse signal to the subhalf-bridge inverter connected to the coil cell which has received theresponse from the power receiver.

In the wireless power transmitter according to the embodiment of thepresent invention, when at least one of the coil cells receives noresponse from a power receiver, the communications and control unit maydisable the sub half-bridge inverters.

In the wireless power transmitter according to the embodiment of thepresent invention, when the wireless power receiver from which theresponse is received is an inductive-type wireless power receiver, thecommunications and control unit may perform power transmission bycontrolling the phase of the second power signal applied to the subhalf-bridge inverter.

In the wireless power transmitter according to the embodiment of thepresent invention, the response from the wireless power receiver maycomprise mode information, and the mode information may indicate whetherthe wireless power receiver is inductive-type or resonant-type.

In the wireless power transmitter according to the embodiment of thepresent invention, the second sub pulse signal may be applied to atleast one of the sub half-bridge inverters, either simultaneously orsequentially.

Another embodiment of the present invention provides a wireless powertransmission method for a wireless power transmitter including a mainhalf-bridge inverter and a plurality of sub half-bridge inverters, themethod including: setting a selection signal to apply a second sub pulsesignal to at least of the one sub half-bridge inverters; transmittingpower to at least one coil cell by applying an enable signal to the atleast one sub half-bridge inverter; and when the at least one coil cellreceives a response from a wireless power receiver, changing theselection signal to apply a first sub pulse signal to the at least onesub half-bridge inverter, wherein the first sub pulse signal is aphase-inverted version of a main pulse signal applied to the mainhalf-bridge inverter and the second sub pulse signal is aphase-controlled version of the main pulse signal.

The wireless power transmission method according to the embodiment ofthe present invention may further include, when the at least one coilcell receives no response from a wireless power receiver, terminatingthe application of the enable signal.

The wireless power transmission method according to the embodiment ofthe present invention may further include, when the at least one coilcell receives a response from a wireless power receiver, determiningwhether the wireless power receiver is inductive-type or resonant-type.

The wireless power transmission method according to the embodiment ofthe present invention may further include, when the wireless powerreceiver is inductive-type, controlling the phase of the second subpulse signal, instead of changing the selection signal.

In the wireless power transmission method according to the embodiment ofthe present invention, the response from the wireless power receiver maycontain mode information, and the mode information may indicate whetherthe wireless power receiver is inductive-type or resonant-type.

In the wireless power transmission method according to the embodiment ofthe present invention, the enable signal is applied to the at least onesub half-bridge inverter, either simultaneously or sequentially.

Advantageous Effects

A wireless power transmitter according to the present invention cancontrol power transmission in a proper way by identifying whether awireless power receiver is resonant-type or inductive-type.

Particularly, the wireless power transmitter according to the presentinvention can identify the type of a wireless power receiver byreceiving mode information from the wireless power receiver. Preferably,the wireless power transmitter may indicate the chargingtype—inductive-type or resonant-type—it supports by transmitting modeinformation.

Moreover, the wireless power transmitter according to the presentinvention can include a main half-bridge inverter and a plurality of subhalf-bridge inverters, and can apply a plurality of sub pulse signals tothe sub half-bridge inverters to apply power for communication or powerfor charging to a plurality of coil cells. With this structure, thewireless power transmitter can switch efficiently between the power forcommunication and the power for charging, and therefore discover andcharge a plurality of wireless power receivers efficiently. Also, withthis structure, circuit complexity can be reduced, and a plurality ofcoil cells can be controlled individually and efficiently.

Additionally, the wireless power transmitter according to the presentinvention can efficiently discover different types of wireless powerreceivers and perform charging control for each type.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless power transmission/reception system according toan embodiment of the present invention.

FIG. 2 is a block diagram showing a power transmission/reception methodaccording to an embodiment of the present invention.

FIG. 3 shows a method of power transfer control in inductive modeaccording to an embodiment of the present invention.

FIG. 4 shows power transmission equipment according to an embodiment ofthe present invention.

FIG. 5 shows power reception equipment according to an embodiment of thepresent invention.

FIG. 6 shows a power transmission method according to an embodiment ofthe present invention.

FIG. 7 shows a configuration packet transmitted by a power receiver anda configuration packet transmitted by a power transmitter according toan embodiment of the present invention.

FIG. 8 shows different operation methods and control flows depending onthe type of a power transmitter and the type of a power receiver.

FIG. 9 shows an ID assignment packet according to an embodiment of thepresent invention.

FIG. 10 shows a frame structure for data communication during powertransfer according to an embodiment of the present invention.

FIG. 11 shows a sync packet according to an embodiment of the presentinvention.

FIG. 12 is a view showing a power transmitter according to an embodimentof the present invention.

FIG. 13 is a view showing a power transmitter according to an embodimentof the present invention.

FIG. 14 shows a main pulse signal, sub pulse signals, and amultiplexer's output pulse signal according to an embodiment of thepresent invention.

FIG. 15 shows a method of operating a wireless power transmitteraccording to an embodiment of the present invention.

FIG. 16 is a view showing a power transmitter according to anotherembodiment of the present invention.

FIG. 17 is a view showing a power transmitter according to anotherembodiment of the present invention.

BEST MODE

Reference will now be made in detail to the preferred embodiments of thepresent invention with reference to the accompanying drawings. Thedetailed description, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present invention, rather than to show the only embodiments that canbe implemented according to the invention. The foregoing descriptionsets forth numerous specific details to convey a thorough understandingof the invention. However, it will be apparent to one skilled in the artthat the invention may be practiced without these specific details.

Most of the terms used herein are general terms that have been widelyused in the technical art to which the present inventive conceptpertains, but some terms are arbitrarily chosen by the applicant in somecases so that their meanings are explained in detail in the followingdescription. Hence, the present invention should be understood with theintended meanings of the terms rather than their simple names andmeanings.

Recently, electromagnetic inductive wireless chargers for variouselectronics including mobile devices—that is, wireless powertransmitters—are being developed. Notably, the WPC (Wireless PowerConsortium) is working toward the standardization of wireless powertransmission/reception technology to enable interoperability acrosswireless power transmitters. In this specification, a mobile devicerefers to an electronic device, such as a mobile phone, tablet PC,laptop, electric toothbrush, etc., that can be handheld and carried. Inthis specification, a mobile device will be described as an example ofan electronic device that receives wireless power; however, this is onlyan embodiment and it should be apparent that the present invention isdirected to a certain electronic device including a wireless powerreceiver.

Recently-developed wireless charging systems support low-powertransmission/reception up to about 5 W. However, with the recent trendtowards larger mobile devices and higher battery capacity, there areproblems with low-power charging, such as long charging times and lowefficiency. Hence, wireless charging systems are currently beingdeveloped to support medium-power transmission/reception up to about 15W. In line with this, wireless charging systems that additionallyincorporate resonant coupling for charging a plurality of electronicdevices are also being developed. The present invention relates to awireless charging system that additionally incorporates resonantcoupling, and is intended to propose a resonant wireless chargingtransmitter/receiver that is compatible with a low-power/medium-powerinductive wireless charging transmitter/receiver.

In what follows, a wireless power transmitter may be abbreviated as apower transmitter or a transmitter, and a wireless power receiver may beabbreviated as a power receiver or a receiver.

FIG. 1 shows a wireless power transmission/reception system according toan embodiment of the present invention.

In FIG. 1, the wireless power transmission/reception system includes amobile device 1010 that wirelessly receives power and a base station1020.

The mobile device 1010 includes a power receiver 1040 that receiveswireless power through a secondary coil and a load 1030 that gets thepower received by the power receiver, stores it, and supplies it to thedevice. The power receiver 1040 may include a power pick-up unit 1080that receives a wireless power signal through the secondary coil andconverts it to electrical energy, and a communications and control unit1090 that controls communications and power signaltransmission/reception (power transfer/reception) to and from a powertransmitter 1050.

The base station 1020 is a device that provides inductive power orresonant power, which may include one or a plurality of powertransmitters 1050 and 1060 and a system unit 1070. The power transmitter1050 may transmit inductive/resonant power and control powertransmission. The power transmitter 1050 may include a power conversionunit 1100 that converts electrical energy to a power signal andtransfers it by creating a magnetic field through primary coil(s), and acommunications and control unit 1110 that controls communications withand power transfer to the power receiver to transfer power at anappropriate level. The system unit 1070 may control other operations ofthe base station, such as input power provisioning, control of multiplepower transmitters, and user interfacing. The base station 1020 may behereinbelow referred to as power transmission equipment.

The power transmitter may control transmission power by controlling anoperating point. The operating point to be controlled may correspond toa combination of frequency (phase), duty cycle, and voltage amplitude.The power receiver may control transferred power by controlling at leastone of frequency (phase) duty cycle/duty ratio, and input voltageamplitude. Also, the power transmitter may supply constant power, andthe power receiver may control receiving power by controlling theresonant frequency.

In what follows, a coil or a coil part may include a coil and at leastone element close to the coil, and be referred to as a coil assembly, acoil cell, or a cell.

In this specification, a power transmitter/receiver may operate ininductive mode or in resonant mode. In inductive mode, the operationmode may be classified into low-power mode and medium-power modeaccording to the amount of power transmitted or received.

In inductive mode, the power transmitter/receiver may transmit andreceive power at a given capacity/level. For example, power transmissionlevels may be classified into low-power transmission, medium-powertransmission, high-power transmission, etc. In this specification,wireless power transmission/reception of up to about 5 W may be referredto as low-power mode transmission/reception, and wireless powertransmission/reception of up to about 15 W may be referred to asmedium-power mode transmission/reception. In some embodiments, low powermay correspond to 0 to 10 W, and medium power may correspond to 10 to 20W.

In resonant mode, a power transmitter may supply power to multiple powerreceivers simultaneously. Accordingly, resonant mode also may bereferred to shared mode. In resonant mode, a power transmitter/receivermay transmit or receive power in a different way from inductive mode.Inductive mode may be referred to as exclusive mode, as opposed toshared mode.

Now, power transmission/reception phases will be described first.

FIG. 2 is a block diagram showing a power transmission/reception methodaccording to an embodiment of the present invention.

In a wireless charging system according to the present invention,wireless charging may be performed in five phases. The five phasesinclude a selection phase S2010, a ping phase S2020, an identification &configuration phase S2030, a negotiation phase S2040, and a powertransfer phase S2050. The negotiation phase S2040 may be omitted inpower transmission/reception in low-power mode. That is, in low-powermode, power transmission/reception is performed in four phases, and thenegotiation phase S2040 may be additionally performed in medium-powermode.

In the selection phase S2010, the power transmitter monitors theinterface surface for the placement and removal of objects. As shown inFIG. 2, the wireless power transmitter may detect a foreign objectcoming into contact by applying a power signal. In other words, thepower transmitter may monitor the presence or absence of a foreignobject by applying a short power signal to the primary coil anddetecting the current in the primary coil, generated by this powersignal. If the power transmitter receives signal strength information(packet) monitored in the selection phase S2010 and detects an objectbased on this information, it may attempt to select whether this objectis a power receiver or only a foreign object (like a key, coin, etc.).In order for the selection to work, the power transmitter may perform atleast one of the ping phase S2020, identification & configuration phaseS2030, and negotiation phase S2040.

In the ping phase S2020, the power transmitter may perform digital pingand wait for a response from the power receiver. Digital ping refers tothe application/transmission of a power signal for detecting andidentifying a power receiver. If the power transmitter discovers a powerreceiver, the power transmitter may extend the digital ping to proceedto the identification & configuration phase S2030.

In the identification & configuration phase S2030, the power transmittermay identify the selected power receiver and obtain the power receiver'sconfiguration information such as the maximum amount of power. In otherwords, the power transmitter may receive identification & configurationinformation and obtain information on the power receiver, and use thisinformation to establish a power transfer contract. This power transfercontract may contain limits for several parameters that characterize thepower transfer in the subsequent power transfer phase S2050.

In the negotiation phase S2040, the power receiver may negotiate withthe power transmitter in order to create an additional power transfercontract. In other words, the power transmitter may receive anegotiation request/information from the power receiver, and thenegotiation phase S2040 may be performed only when the receiver isidentified as a medium-power receiver in the identification &negotiation phase S2030. In the negotiation phase S2040, additionalparameters such as the power transmitter's guaranteed power level andthe power receiver's maximum power may be negotiated. If the powerreceiver is a low-power receiver, the negotiation phase S2040 may beomitted, and the power transmitter may proceed directly to the powertransfer phase S2050 from the identification & configuration phaseS2030.

In the power transfer phase S2050, the power transmitter wirelesslyprovides power to the power receiver. The power transmitter may receivecontrol data for the transmitting power and control the power transferbased on the control data. A violation of any of the stated limits onany of those parameters in the power transfer contract during powertransfer causes the power transmitter to abort the powertransfer—returning the system to the selection phase S2010.

FIG. 3 shows a method of power transfer control in inductive modeaccording to an embodiment of the present invention.

A power transmitter 3010 and power receiver 3020 in FIG. 3 each mayinclude a power conversion unit 3030 and a power pick-up unit 3040, asillustrated in FIG. 1.

In the power transfer phase S2050 in the above-stated inductive mode,the power transmitter and the power receiver may control the amount ofpower transfer by performing communication along with powertransmission/reception. The power transmitter and the power receiveroperate at a specific control point. The control point refers to thecombination of voltage and current provided at the output of the powerreceiver during power transfer.

More specifically, the power receiver selects a desired control point—adesired output current and/or voltage, a temperature measured particularposition in the mobile device, etc. In addition, the power receiverdetermines its actual control point at which it is currently operating.Using the desired control point and actual control point, the powerreceiver may calculate a control error value and transmit this controlerror value as a control error packet to the power transmitter.

Then, the power transmitter may use the received control error packet tocontrol power transfer by setting and controlling a new operatingpoint—amplitude, frequency, and duty cycle. Accordingly, the controlerror packet is sent and received at regular time intervals in the powertransfer phase, and in an embodiment, the power receiver may set thecontrol error value to a negative number if it wants to decrease thecurrent in the power transmitter and set the control error value to apositive number if it wants to increase the current in the powertransmitter. In this way, in inductive mode, the power receiver maycontrol power transfer by sending a control error packet to the powertransmitter.

The resonant mode to be described below may operate in a different wayfrom inductive mode. In resonant mode, a single power transmitter has toserve multiple power receivers simultaneously. However, in the controlof power transfer in the above-stated inductive mode, transferred poweris controlled via communication with a single power receiver, so it maybe difficult to control the power transfer to additional powerreceivers. Accordingly, in the resonant mode according to the presentinvention, the power transmitter may transfer basic power common topower receivers, and the power receiver may control its resonantfrequency to control the amount of received power. However, the methodexplained with reference to FIG. 3 is not completely excluded from theoperation in resonant mode, but additional transmission power controlmay be performed in the method of FIG. 3.

FIG. 4 shows power transmission equipment according to an embodiment ofthe present invention.

In FIG. 4, the power transmission equipment 4010 may include at leastone among a cover 4020 that covers a coil assembly, a power adaptor 4030that supplies power to a power transmitter, a power transmitter 4040that transmits wireless power, or a user interface 4050 that providesinformation about the progress of power transfer and other relevantinformation. Particularly, the user interface 4050 may be optionallyincluded in the power transmission equipment 4010 or may be included asanother user interface 4050 for the power transmission equipment 4010.

The power transmitter 4040 may include at least one among a coilassembly 4060, an impedance matching circuit 4070, an inverter 4080, acommunication unit 4090, or a control unit 4100.

The coil assembly 4060 may include at least one primary coil thatgenerates a magnetic field, and also may be referred to a coil cell.

The impedance matching circuit 4070 may provide impedance matchingbetween the inverter and the primary coil(s). The impedance matchingcircuit 4070 may generate a resonance at a frequency suitable to boostthe primary coil current. In a multi-coil power transmitter, theimpedance matching circuit may additionally include a multiplexer thatroutes a signal from the inverter to a subset of the primary coils. Theimpedance matching circuit also may be referred to as a tank circuit.

The inverter 4080 may convert DC input to an AC signal. The inverter4080 may operate as a half-bridge inverter or a full-bridge inverter togenerate a pulse wave of an adjustable frequency and a duty cycle. Also,the inverter may include a plurality of stages to adjust the inputvoltage level.

The communication unit 4090 may communicate with a power receiver. Thepower receiver performs load modulation in order to communicate arequest or other information to the power transmitter. Accordingly, thepower transmitter may monitor the amplitude and/or phase of the currentand/or voltage in the primary coil, in order to demodulate datatransmitted by the power receiver using the communication unit 4090.Furthermore, the power transmitter may control output power so as totransmit data via the communication unit 4090 by FSK (Frequency-shiftkeying).

The control unit 4100 may control the power transmitter's communicationand power transfer. The control unit 4100 may control power transmissionby adjusting the above-stated operating point. The operating point maybe determined by at least one among operating frequency, duty cycle, andinput voltage, for example.

The communication unit 4090 and the control unit 4100 may be provided asdiscrete units, devices, or chipsets or as a single unit, device, orchipset, as shown in FIG. 1.

FIG. 5 shows power reception equipment according to an embodiment of thepresent invention.

In FIG. 5, power reception equipment 5010 may include at least one amonga user interface 5020 that provides information about the progress ofpower transfer and other relevant information, a power receiver 5030that receives wireless power, and a base 5050 that supports and covers aload circuit 5040 or coil assembly. Particularly, the user interface5020 may be optionally included in the power reception equipment 5010 ormay be included as another user interface 5020 for the power receptionequipment.

The power receiver 5040 may include at least one of a power converter5060, an impedance matching circuit 5070, a coil assembly 5080, acommunication unit 5090, or a control unit 5100.

The power converter 5060 may convert AC power, received from a secondarycoil, to a voltage and current suitable for the load circuit. In anembodiment, the power converter 5060 may include a rectifier. Further,the power converter may adapt a reflected impedance of the powerreceiver.

The impedance matching circuit 5070 may provide impedance matchingbetween the secondary coil and a combination of the power converter 5060and the load circuit 5070. In an embodiment, the impedance matchingcircuit may generate a resonance of around 100 kHz which may enhancepower transfer.

The coil assembly 5080 includes at least one secondary coil and,optionally, may further include an element for shielding the metal partof a receiver against a magnetic field.

The communication unit 5090 may perform load modulation in order tocommunicate a request and other information to the power transmitter. Tothis end, the power receiver 5030 may switch a resistor or capacitor onor off so that reflected impedance is changed.

The control unit 5100 may control received power. To this end, thecontrol unit 5100 may determine/calculate the difference between theactual operating point of the power receiver 5030 and a desiredoperating point. Furthermore, the control unit 5100 may adjust/reducethe difference between the actual operating point and the desiredoperating point by making a request to adjust the reflected impedance ofthe power transmitter and/or the operating point of the powertransmitter. If such a difference is minimized, optimal power receptioncan be achieved.

The communication unit 5090 and the control unit 5100 may be provided asdiscrete units, devices, or chipsets or as a single unit, device, orchipset, as shown in FIG. 1.

Hereinafter, a power transmission/reception system and method inresonant mode will be further described.

As stated above, the power transmission/reception system may operate ininductive mode and resonant mode, and, in inductive mode, it may operatein low-power mode and medium-power mode. In the present invention,however, a power transmitter may support receivers in both inductive andresonant modes. That is, the power transmitter may transmit powerdepending on the type of a discovered receiver,—that is, in resonantmode if the receiver is a resonant-type receiver and in inductive modeif the receiver is an inductive-type receiver. In the case of theinductive-type receiver, the power transmitter may transmit power inlow-power mode and medium-power mode, depending on whether the receiveris a low-power receiver or medium-power receiver. To this end, the powertransmitter may determine the type of a power receiver.

Now, a description will be given of a method in which a powertransmitter and a power receiver detect whether the other end is inresonant mode or in inductive mode and perform wireless chargingdepending on their operation mode.

First of all, a resonant-type power transmitter determines the type of apower receiver by parsing the information contained in a packet receivedfrom the power receiver. Also, a resonant-type power receiver is drivenin inductive mode until it reaches the negotiation phase, and determinesthe type of the power transmitter by parsing the information containedin a packet received from a power transmitter in the negotiation phase.If the power transmitter is in resonant mode, based on the parsedinformation, the resonant-type power receiver may change its operationmode from inductive mode to resonant mode. The power receiver inresonant mode may perform the power transfer phase in resonant mode orinductive mode, depending on the type of the power transmitter.

The information a transmitter and a receiver transmit to identify theirtype may be called mode information. In other words, the modeinformation may indicate whether the transmitter and the receiveroperate in resonant mode and/or inductive mode.

As stated above, a power receiver may transmit a configuration packet toa transmitter in the identification & configuration phase. If theconfiguration packet indicates a request for the negotiation phase, thepower transmitter may proceed to the negotiation phase. That is, it canbe concluded that the receiver is in medium-power mode during inductivemode. If the configuration packet does not indicate a request for thenegotiation phase, the power transmitter may proceed directly to thepower transfer phase.

FIG. 6 shows a power transmission method according to an embodiment ofthe present invention.

FIG. 6 shows in detail the identification & configuration phase andnegotiation phase of FIG. 2, particularly, a method in which a powertransmitter and a power receiver identify each other's type anddetermine the operation mode. The identification & configuration phaseS6010 and the negotiation phase S6020 correspond to the identification &configuration phase S2030 and negotiation phase S2040 of FIG. 2,respectively, and a description of this will be omitted to avoidredundancy but a supplementary explanation will be given instead.

In the identification & configuration phase S6010, the power receivertransmits an identification packet and a configuration packet to thepower transmitter.

The identification packet contains the version (major/minor versions),manufacturer code, and basic device identifier of the power receiver.The power transmitter may identify the power receiver through theidentification packet.

The configuration packet contains information about the configuration ofthe power receiver. In an embodiment of the present invention, theconfiguration packet may contain negotiation phase request information(Neg field). If the negotiation phase request information is set to 0(Neg=0), the power transmitter may proceed directly to the powertransfer phase without going through the negotiation phase. If thenegotiation phase request information is set to 1 (Neg=1), the powertransmitter may proceed to the negotiation phase. In an embodiment ofthe present invention, the configuration packet contains modeinformation. The mode information may indicate whether the powerreceiver supports only inductive mode or both inductive and resonantmodes.

In the identification & configuration phase S6010, the powertransmitter, upon receiving an identification packet and a configurationpacket, may identify the type of the power receiver through theconfiguration packet. As stated above, the power transmitter mayidentify whether the power receiver is a low-power inductive-typereceiver or a medium-power inductive-type receiver or a resonant-typereceiver, by using the negotiation phase request information. Then, thepower transmitter may identify whether the power receiver is amedium-power inductive-type receiver or a resonant-type receiver, byparsing the mode information.

If the power receiver is a low-power inductive-type receiver, the powertransmitter may proceed to the power transfer phase without goingthrough the negotiation phase S6020. If the power receiver ismedium-power inductive-type or resonant-type, the power transmitter maytransmit an acknowledgment (ACK) to the power receiver and proceed tothe negotiation phase S6020.

In the negotiation phase S6020, an identification packet and aconfiguration packet may be transmitted to the power transmitter orpower receiver. The identification packet transmitted by the powertransmitter may contain version information (major/minor versions) andmanufacturer information. The configuration packet transmitted by thepower transmitted may contain power information and mode information.

In the negotiation phase S6020, the power transmitter performs powerallocation and operation mode decision. If the power transmitteroperates in resonant mode, it may perform ID assignment for at least onepower receiver.

The power receiver may identify the type of the power transmitter basedon the mode information received from the power transmitter. Since thepower transmitter has proceeded to the negotiation phase, it may beidentified as medium-power inductive-type or resonant-type. Then, thepower receiver may identify whether the power transmitter isinductive-type or resonant-type, based on the mode information receivedin the negotiation phase S6020.

A medium-power inductive-type receiver may perform power reception andcharging at full-power capacity supported for it. A resonant-typereceiver may perform power reception and charging by selecting a powercontrol method depending on the type of the transmitter. If the powertransmitter is medium-power inductive-type, the power receiver mayperform power reception and charging at full-power capacity.

FIG. 7 shows a configuration packet transmitted by a power receiver anda configuration packet transmitted by a power transmitter according toan embodiment of the present invention.

(a) of FIG. 7 shows the configuration packet the power receivertransmits in the above-stated identification & configuration phase.Descriptions of the fields contained in the configuration packet of (a)of FIG. 7 are as follows.

-   -   Power Class field: This field contains an unsigned integer value        associated with a guaranteed power value.    -   Maximum Power field: This field indicates the maximum amount of        power, which the power receiver expects to provide at the output        of the rectifier.    -   Prop field: This field indicates the method of controlling power        transfer in the power transfer phase.    -   Neg field (negotiation phase request information): If this field        is set to a value of 1, the power transmitter transmits an ACK        message and proceeds to the negotiation phase. If this field is        set to a value of 0, the power transmitter proceeds to the power        transfer phase without going through the negotiation phase.    -   FSK polarity (FSKPolarity) field: This field indicates whether        the modulation polarity of the transmitter is a default value or        a reversed value.    -   FSK depth (FSKDEpth) field: This field indicates the modulation        depth of the transmitter.    -   Count field: This field indicates the number of optional        configuration packets that the power receiver transmits in the        identification & configuration phase.    -   Window Size field: This field indicates the window size for        averaging received power.    -   Window Offset field: This indicates the interval between the        window for averaging received power and a received power packet        transmission.    -   Operation Mode (OP Mode) field: The above-stated mode        information that indicates the operation mode supported by the        power receiver. In an embodiment, if the operation mode field        has a value of 0, this indicates inductive mode (=exclusive        mode), and if the operation mode field has a value of 1, this        indicates resonant mode (=shared mode).

(b) of FIG. 7 shows the configuration packet the power transmittertransmits in the above-stated negotiation phase. Descriptions of thefields contained in the configuration packet of (b) of FIG. 7 are asfollows.

-   -   Guaranteed Power Class field: This field indicates the power        receiver's power class. In an embodiment, a low-power        transmitter may have a field value of 1, and a medium-power        receiver may have a field value of 0.    -   Guaranteed Power field: This field indicates the amount of power        for an appropriate reference power receiver that the power        transmitter guarantees.    -   Potential Power Class field: This field indicates the power        class of the power transmitter. In an embodiment, a low-power        transmitter may have a field value of 1, and a medium-power        receiver may have a field value of 0.    -   Potential Power field: This field indicates the amount of power        that the power transmitter can potentially transfer to an        appropriate reference power receiver.    -   Operation Mode (OP Mode) field: The above-stated mode        information that indicates the operation mode supported by the        power transmitter. In an embodiment, if the operation mode field        has a value of 0, this indicates inductive mode (=1:1 charging        mode), and if the operation mode field has a value of 1, this        indicates resonant mode (=shared mode).

FIG. 8 shows different operation methods and control flows depending onthe type of a power transmitter and the type of a power receiver.

(a) of FIG. 8 shows the data flow between a low-power inductive-typepower transmitter and each power receiver type.

In (a) of FIG. 8, since the power transmitter is low-power inductivetype, it only supports low-power inductive type power transmission.Thus, a medium-power inductive-type receiver and a resonant-typereceiver, as well as a low-power inductive-type receiver, operate inlow-power inductive mode. Accordingly, the negotiation phase is omitted,as stated above, and in the digital ping phase, identification &configuration phase, and power transfer phase, data is transmitted froma receiver to the transmitter, and the receiver controls overalloperation.

(b) of FIG. 8 shows the data flow between a medium-power inductive-typepower transmitter and each power receiver type.

In (b) of FIG. 8, since the power transmitter is medium-power inductivetype, it supports the low-power inductive-type power receiver and themedium-power inductive-type power receiver. Thus, if the power receiveris a low-power inductive receiver, it may operate in low-power inductivemode without going through the negotiation phase, and if the powerreceiver is a medium-power inductive receiver or a resonant receiver, itmay operate in low-power inductive mode after going through thenegotiation phase.

If the power receiver is driven in medium-power inductive mode, thepower transmitter may transmit ID information or configurationinformation to the power receiver in the negotiation phase, therebyallowing for bidirectional communication in the negotiation phase. Onthe other hand, in the other phases, the transmitter transmits data tothe receiver, and the overall operation of power charging is controlledby the receiver.

(c) of FIG. 8 shows the data flow between a resonant-type powertransmitter and each power receiver type.

In (c) of FIG. 8, since the power transmitter is resonant-type, itsupports both the inductive-type power receiver and the resonant-typepower receiver for the respective type of the power receiver. Thus, thelow-power inductive receiver operates in low-power inductive mode, themedium-power inductive receiver operates in medium-power inductive mode,and the resonant-type receiver operates in resonant mode, respectively.In the case of power transmission between a resonant transmitter and aresonant receiver, bidirectional data communication is performed in thepower transfer phase as well. In the case of power transfer in resonantmode, the receiver controls received power by controlling its resonantfrequency, and may further control received power by making a request tocontrol the operating point of the power transmitter.

FIG. 9 shows an ID assignment packet according to an embodiment of thepresent invention.

A resonant-type power transmitter is able to charge multipleresonant-type power receivers simultaneously. But, it is necessary toassign IDs to the power receivers for communication when transmittingpower to multiple resonant-type power receivers.

In FIG. 9, the ID field indicates ID information of at least one powerreceiver detected. When power transmission/reception is performed inresonant mode, the power receiver may send an ID request to the powertransmitter. In this case, the power transmitter may assign an ID to thepower receiver, and transmit the assigned ID information, contained inthe ID assignment packet of FIG. 9, to the power receiver.

FIG. 10 shows a frame structure for data communication during powertransfer according to an embodiment of the present invention.

In resonant mode, a power transmitter may act as a master and transmit async signal to a power receiver, and the power receiver may act as aslave and transmit a response signal to the sync signal. Thecommunication between the power transmitter and the power receiver maybe terminated if the power transmitter sends no sync signal. The syncsignal, contained in a sync packet, and the response signal, containedin a response packet, may be allocated to a time slot in a time-divisionmultiplexed frame, as in the structure of FIG. 10.

In resonant mode, the power transmitter has to communicate with multiplepower receivers, and therefore may allocate time slots contained in aframe for communication to the power receivers. In this case, dependingon the method of sync signal allocation, the power transmitter may useone sync signal per frame, as in (a) of FIG. 10, or may use multiplesync signals by allocating a sync signal to each time slot of a frame,as in (b) of FIG. 10. The allocation of time slots to power receiversmay be performed using the ID and ID assignment packet explained withreference to FIG. 9.

The power transmitter may transmit a sync packet and receive statusinformation of the power receiver as a response packet to the syncpacket. The status information may include received power information ora power transmission termination request. For security purpose, thepower receiver may transmit OV/OC/OT information even without receivinga sync signal.

FIG. 11 shows a sync packet according to an embodiment of the presentinvention.

A power transmitter may transmit a sync packet in order to receive aresponse from a particular power receiver. As shown in FIG. 11, the syncpacket may contain an address ID (ADDR ID) field and a request field.

The address ID (ADDR ID) field may identify the target power receiverthe power transmitter makes a request for response to. Address IDinformation for identifying the target power receiver may correspond tothe ID information assigned through the ID assignment packet shown inFIG. 9. The power transmitter may use an address ID requesting responsesfrom all power receivers currently being charged, as well as the addressID of a particular power receiver.

In an embodiment, if the value of the address ID field is 111b, allpower receivers currently being charged may transmit a response in anallocated time slot. If the value of the address ID field indicates aparticular power receiver, only that power receiver may transmit aresponse.

The request field may indicate the information the power transmitterrequests the power receiver to send.

In an embodiment, the request field may request for the followingresponses depending on the field value.

If the value of the request field is 0001b, the power transmitter mayrequest the power receiver for a status report. The status report maycorrespond to a received power packet, a power transmission terminationpacket, etc. If the value of the request field is 0010b, the powertransmitter may make a request for renegotiation for power distribution.In other words, the power transmitter may request the power receiver toperform the negotiation phase again for power reallocation.Alternatively, the power transmitter may make a re-request for IDinformation, etc.

In another embodiment, the request field may request for the followingresponses depending on the field value.

If the value of the request field is 0001b, the power transmitter mayrequest the power receiver to transmit received power information. Ifthe value of the request field is 0010b, the power transmitter mayrequest the power receiver to transmit rectified voltage information. Ifthe value of the request field is 0011b, the power transmitter mayrequest the power receiver to transmit a power transfer terminationpacket. If the value of the request field is 0100b, the powertransmitter may request for renegotiation for power distribution. Inother words, the power transmitter may request the power receiver toperform the negotiation phase again for power reallocation. If the valueof the request field is 0101b, the power transmitter may request thepower receiver to transmit ID information.

Hereinafter, a power transfer method for a power transmitter accordingto an embodiment of the present invention will be described in moredetail.

The present invention is directed to provide a power transmitter capableof charging both an inductive power receiver and a resonant powerreceiver. As stated above, in the case of the inductive power receiver,the power transmitted by the power transmitter is controlled; whereas,in the case of the resonant power receiver, the power received by thepower receiver is controlled. Accordingly, the power transmitted inresonant mode may be set to be higher or stronger than the powertransmitted in inductive mode. Now, the design of an inverter for easilysupporting both modes and the corresponding power transmission methodwill be further explained below.

FIG. 12 is a view showing a power transmitter according to an embodimentof the present invention.

The power transmitter of FIG. 12 will be described to give asupplementary explanation of the power transmitter of FIGS. 1 through 4.The above-described components of the power transmitter which are notshown in FIG. 12 are omitted for convenience of explanation, and may beincluded or excluded depending on the configuration.

In FIG. 12, the power transmitter may include a selection unit 12010, acommunications and control unit 12020, and a power conversion unit12030.

The selection unit 12010 is a circuit that detects the location orpresence/absence of a power receiver, and may be optionally provided.

The communications and control unit 12020 communicates with a powerreceiver, executes the relevant power control algorithms and protocols,and drives the frequency of an AC waveform to control the powertransfer. Particularly, in the present invention, the communications andcontrol unit 12020 may control the operation of a sub half-bridgeinverter 12070 and a pulse signal PWM for driving the sub half-bridgeinverter 12070.

In the embodiment of FIG. 12, the power conversion unit 12030 is aninverter that converts DC input to an AC waveform that drives a resonantcircuit, and may include a main half-bridge inverter 12040 to which amain pulse signal is applied, a sub half-bridge inverter 12070 to whicha sub pulse signal is applied, a coil cell 12060 that generates amagnetic field, a current sensor 12050 that monitors the current throughthe coil cell. The coil cell 12060 may include a coil and a resonantcapacitor.

A power transmitter according to the present invention may include aplurality of coil cells to charge multiple power receiverssimultaneously. In this case, it is difficult to perform power controlon each of the power receivers being charged simultaneously if only asingle inverter is used for the plurality of coil cells. Moreover,although using multiple inverters to provide each coil cell with aninverter may allow for power control on each of the power receiversbeing charged simultaneously, it may add circuit complexity and increasethe cost of circuit manufacture. Accordingly, the present inventionproposes a power transmitter capable of controlling multiple powerreceivers more easily while reducing circuit complexity, by designingthe power transmitter to have a main half-bridge inverter to which amain pulse signal is applied and to use a plurality of sub half-bridgeinverters for a plurality of coil cells.

FIG. 13 is a view showing a power transmitter according to an embodimentof the present invention.

FIG. 13 shows the power transmitter of FIG. 12 in more detail.

In FIG. 13, the power transmitter includes a main half-bridge inverter13010, a current sensor 13020, N coil cells 13030-1 to 13030-N, N subhalf-bridge inverters 13040-1 to 13040-N, N multiplexers (MUX) 13050-1to 13050-N, N enable terminals 13060-1 to 13060-N, N selection terminals(SEL) 13070-1 to 13070-N, and a communications and control unit 13080.

A main pulse signal (main PWM) may be applied to the main half-bridgeinverter 13010, and a first sub pulse signal (sub PWM 1) or second subpulse signal (sub PWM 2) may be applied to each of the sub half-bridgeinverters 13040. The multiplexers 13050 may apply the first sub pulsesignal or second sub pulse signal to the sub half-bridge inverters 13040according to a selection input from the selection terminals 13070. Insome applications, two or more sub pulse signals may be selectivelyapplied.

The communications and control unit 13080 may apply an enable signal ordisable signal to the enable terminals 13060 to enable or disable thesub half-bridge inverters 13040, respectively. In other words, thecommunications and control unit 13080 may apply an enable signal orterminate the application of the enable signal to enable or disable thesub half-bridge inverters 13040. Moreover, the communications andcontrol unit 13080 may apply a selection signal to the selectionterminals 13070 to select an output from the multiplexers 13050. Theenable terminals 13060 and the selection terminals 13070 are controlledby the communications and control unit 13080, and may be optionallyincluded depending on the design of the transmitter.

The power transmitter of FIG. 13 has the basic function of driving themain half-bridge inverter 13010, and may control the current flowingthrough each coil cell by enabling or disabling each sub half-bridgeinverter or selectively applying a sub pulse signal to each subhalf-bridge inverter, thereby providing efficient control of powertransfer. A method of operation of an additional power transmitter willbe described below in more detail.

FIG. 14 shows a main pulse signal, sub pulse signals, and amultiplexer's output pulse signal according to an embodiment of thepresent invention.

First of all, the main pulse signal (main PWM) may be a pulse signalwith a particular amplitude and frequency. In this regard, the sub pulsesignals are generated using the main pulse signal. That is, the firstsub pulse signal (sub PWM 1) may be a phase-inverted version of the mainpulse signal, i.e., a signal with a phase difference of 180° withrespect to the main pulse signal, and the second pulse signal (sub PWM2) may be a phase-controlled version of the main pulse signal.

Configuring the main pulse signal and the sub pulse signals in this wayoffers the advantage of using the following method of operation. Asstated above, the main pulse signal is applied to the main half-bridgeinverter, and the first sub pulse signal or second sub pulse signal isapplied to the sub half-bridge inverters. If the first sub pulse signalis applied, the coil can provide its maximum power by the phasedifference with respect to the main pulse signal. On the other hand, ifthe second sub pulse signal is applied, the coil can provide less powerthan the maximum by the phase difference with respect to the main pulsesignal.

When the second sub pulse signal is applied, the amount of transferredpower may differ depending on the degree of phase control. The closerthe phase difference to be controlled is to 180°, the closer the amountof transferred power gets to the maximum, and the closer the phasedifference to be controlled is to 0°, the smaller the amount oftransferred power gets. In an embodiment, the second sub pulse signalmay be a phase-controlled version of the main pulse signal with a phasedifference of −90° to +90° with respect to the main pulse signal. Thisis because it is more efficient to control the first sub pulse signal ifthe phase difference is out of this range.

The sub pulse signals are switched by the multiplexer. The multiplexermay switch and output the sub pulse signals according to a selectionsignal. As in the embodiment of FIG. 14, if the communications andcontrol unit applies a selection signal 1, the multiplexer may outputthe first sub pulse signal, and if the communications and control unitapplies a selection signal 0, the multiplexer may output the second subpulse signal.

The enable signal is a signal that enables actual power transmission.FIG. 13 illustrates that current is applied only when the enable signalis applied to the coil cells while the main pulse signal is applied tothe main half-bridge inverter, thereby enabling power transfer.

As illustrated in FIG. 14, if the first sub pulse signal is applied tothe sub half-bridge inverters, the coil cells may transfer high power,and if the second sub pulse signal is applied to the sub half-bridgeinverters, the coil cells may transfer low power. In this specification,the power output by the coil cells may be referred to as power forcharging if the first sub pulse signal is applied, and power forcommunication if the second sub pulse signal is applied. The power forcommunication may be used to discover a power receiver by applying aping or digital ping when driving the circuit or to performcommunication with the power receiver. Needless to say, althoughcommunication power may be used for charging by performing additionalphase control, the second sub pulse signal may be referred to as powerfor communication for convenience of explanation.

By using the configuration shown in FIGS. 13 and 14, the powertransmitter may discover at least one power receiver and perform powertransmission by efficiently controlling a plurality of coil cells. Amethod of controlling the power transmitter of FIG. 13 using the signalsof FIG. 14 will be described below with reference to FIG. 15.

FIG. 15 shows a method of operating a wireless power transmitteraccording to an embodiment of the present invention.

Although the operations shown in FIG. 15 are controlled by thecommunications and control unit, a description of them will be made onthe assumption that they are controlled by a wireless power transmitter,for convenience of explanation. Also, FIG. 15 shows a method in which apower transmitter discovers a power receiver and performs otherprocesses prior to power transmission by using the circuit of FIG. 13and the pulse signals of FIG. 14. At the start of the method of FIG. 15,it is assumed that the power transmitter has not applied an enabledsignal to any of a plurality of coil cells.

The power transmitter may set a selection signal to apply a second subpulse signal (S15010). In other words, the power transmitter may set aselection signal for outputting the second sub pulse signal and apply itto a multiplexer. As in the above-described embodiment, if the selectionsignal is set to 0, the second sub pulse signal may be applied, and thecommunications and control unit may apply the selection signal 0 to themultiplexer via a selection terminal and output a desired second subpulse signal.

The power transmitter may apply an enable signal to the sub half-bridgeinverter of the first coil cell and transmit power (S15020). Thetransmitted power is power for communication, and may correspond to theabove-mentioned ping or digital ping. Alternatively, the transmittedpower may be used for the above-described data transmission by the powertransmitter. In other words, the second sub pulse signal may be appliedto the sub half-bridge inverter so that the first coil cell can transmitlow power for driving the circuit and discovering a receiver.

The power transmitter may receive a response from the power receiver(S15030). The power transmitter may discover a power receiver by sensinga change across the primary coil caused by the applied power forcommunication by using a current sensor, and detect a response from thepower receiver. The step 15030 shown in FIG. 15 involves the discoveryof a power receiver and the reception of a response from the powerreceiver. This step may correspond to at least one of the identificationand configuration phase and negotiation phase of FIG. 2.

Upon receiving a response from the power receiver, the power transmittermay change the selection signal setting to apply a first sub pulsesignal (S15040). In the above-described embodiment, the communicationsand control unit may apply a first sub pulse signal to the subhalf-bridge inverter by changing the selection signal to 1. As the firstsub pulse signal is applied to the sub half-bridge inverter, the firstcoil cell may initiate power transfer by transmitting charging power.

If no response is received from the power receiver, the powertransmitter may terminate the application of the enable signal (S15050).This is because, since no power receiver is discovered, the powertransmitter may conclude that the first coil cell has no power receiverattached to it which requires charging.

In FIG. 15, the steps S15010 to 15050 may be performed for each coilcell. Accordingly, the power transmitter may perform the steps of FIG.15 for the second coil cell and then all the way to the Nth coil cell(last coil cell) in the same manner, and then end the sequence. Then,after a certain time interval, or if a foreign object is discovered byan analog ping, the steps of FIG. 15 may be performed over again. Thepower transmitter may perform the steps of FIG. 15 only for coil cellswhich are not being charged with electricity or only for coil cellswhich have discovered a foreign object. Then, the second sub pulsesignal may be time-division-multiplexed and supplied to only one coil ata time.

In addition, if a response is received from the power receiver (S15030),the power transmitter may operate differently depending on the type ofthe power receiver. If the power receiver is a resonant-type powerreceiver, the power transmitter may change the selection signal settingto apply the first sub pulse signal, as explained with reference to FIG.15 (S15040). If the power receiver is an inductive-type power receiver,the power transmitter may transmit power by controlling the phase of thesecond sub pulse signal, without changing the selection signal setting.

For a resonant-type power receiver, the power transmitter may transmithigh power and the power receiver then can adjust the resonant frequencyand receive an appropriate amount of power. On the other hand, for aninductive-type power receiver, the power transmitter has to transmit anappropriate amount of power, because adjusting power from low power tohigh power is more advantageous in terms of the circuit and thestability of power transfer.

In an embodiment, a response from the power receiver may contain theabove-described mode information. The power transmitter may parsereceived mode information and determine whether the power receiver is aresonant-type power receiver or inductive-type power receiver.

FIG. 16 is a view showing a power transmitter according to anotherembodiment of the present invention.

The configuration of the power transmitter of FIG. 16 is as illustratedin FIG. 12. But, the configuration of the current sensor 16010 isdifferent from what is illustrated in FIG. 12, which will be explainedin more detail with reference to FIG. 17. All the other parts, exceptfor the position and configuration of the current sensor, are the sameas described with reference to FIG. 12.

FIG. 17 is a view showing a power transmitter according to anotherembodiment of the present invention.

FIG. 17 shows the power transmitter of FIG. 16 in more detail.

The power transmitter shown in FIG. 17 includes the same sub units asthe power transmitter shown in FIG. 13. That is, the power transmitterincludes a main half-bridge inverter, N coil cells, N sub half-bridgeinverters, N multiplexers, N enable terminals, N selection terminals,and a communications and control unit. However, FIG. 17 illustratesthat, instead of one current sensor connected to the main half-bridgeinverter shown in FIG. 13, N current sensors are included between eachcoil cell and each sub half-bridge inverter. All the other parts are thesame as those shown in FIG. 13, except for the difference inconfiguration, and the difference in the configuration of currentsensors will be described below.

The power transmitter of FIG. 17 may perform communication and controlfor each coil cell since current sensors are respectively connected tothe coil cells. In other words, the method of FIG. 15 may be performedfor all the coil cells at once, rather than one coil cell at a time insequence.

In the method of FIG. 15, the power transmitter of FIG. 17 may transmitpower for communication to all the coil cells by applying an enablesignal to all the coil cells, i.e., all the sub half-bridge inverters,at once. Also, the power transmitter of FIG. 17 may transfer power bydiscovering a power receiver or communicating with the power receiver bythe current sensors 17010-1 to -N and applying the first sub pulsesignal only to coil cells which have acknowledged a response.

The power transmitter of FIG. 17 may operate differently depending onthe type of the power receiver discovered in each coil cell, asexplained with reference to FIG. 15. If a result of communication showsthat the power receiver is inductive-type, the power transmitter of FIG.17 may perform power transmission by controlling the phase of thealready applied second sub pulse signal, without applying the first subpulse signal. It should be noted that the phase of the first sub pulsesignal may be shifted to a phase (e.g., the initial phase of the secondsub pulse signal) that allows for initial power transmission, and thephase-shifted first sub pulse signal may be supplied to the other coils.

Using the power transmitter shown in FIGS. 16 and 17 enables multiplepower receivers to be charged simultaneously and allows forcommunications with and control of each power receiver. Accordingly,multiple inductive-type receivers, as well as multiple resonant-typereceivers, can be charged simultaneously, and both the inductive-typereceivers and the resonant-type receivers can be charged simultaneously.Particularly, the power transmitter shown in FIGS. 16 and 17 supports asmany inductive-type receivers as the number of sub pulse signals sinceit uses two or more sub pulse signals. That is, N inductive-typereceivers can be charged simultaneously by controlling them individuallywith the use of N sub pulse signals.

It will be apparent to those skilled in the art that numerousmodifications and variations can be made to the invention withoutdeparting from the spirit or scope of the present invention. Thus, theinvention is intended to cover modifications and variations provided inthe appended claims and their equivalent ranges.

Both the device and method inventions are mentioned herein, thedescription of both the device and method inventions can becomplementary to each other.

Various embodiments have been described in the best mode for carryingout the present invention.

INDUSTRIAL APPLICABILITY

The present invention is used in a series of wireless chargingtechnologies.

It will be apparent to those skilled in the art that numerousmodifications and variations can be made to the invention withoutdeparting from the spirit or scope of the present invention. Thus, theinvention is intended to cover modifications and variations provided inthe appended claims and their equivalent ranges.

The invention claimed is:
 1. A wireless power transmitter which iscapable of charging a plurality of wireless power receivers, thewireless power transmitter comprising: a plurality of coil cells; a mainhalf-bridge inverter to which a main pulse signal is applied; aplurality of sub half-bridge inverters to which a first sub pulse signalor a second sub pulse signal is applied; a current sensor configured tomonitor the current of the coil cells; and a communications and controlunit configured to control the pulse signals applied to the mainhalf-bridge inverter and sub half-bridge inverters and communicate withthe wireless power receivers, wherein the sub half-bridge inverters arerespectively connected to the coil cells, and the first sub pulse signalis a phase-inverted version of the main pulse signal and the second subpulse signal is a phase-controlled version of the main pulse signal. 2.The wireless power transmitter of claim 1, wherein the communicationsand control unit applies the second sub pulse signal to at least one ofthe sub half-bridge inverters to discover a power receiver.
 3. Thewireless power transmitter of claim 2, wherein, when at least one of thecoil cells receives a response from a power receiver, the communicationsand control unit performs power transmission by applying the first subpulse signal to the sub half-bridge inverter connected to the coil cellwhich has received the response from the power receiver.
 4. The wirelesspower transmitter of claim 2, wherein, when at least one of the coilcells receives no response from a power receiver, the communications andcontrol unit disables the sub half-bridge inverters.
 5. The wirelesspower transmitter of claim 3, wherein, when the wireless power receiverfrom which the response is received is an inductive-type wireless powerreceiver, the communications and control unit performs powertransmission by controlling the phase of the second power signal appliedto the sub half-bridge inverter.
 6. The wireless power transmitter ofclaim 3, wherein the response from the wireless power receiver comprisesmode information, and the mode information indicates whether thewireless power receiver is inductive-type or resonant-type.
 7. Thewireless power transmitter of claim 2, wherein the second sub pulsesignal is applied to at least one of the sub half-bridge inverters,either simultaneously or sequentially.
 8. A wireless power transmissionmethod for a wireless power transmitter comprising a main half-bridgeinverter and a plurality of sub half-bridge inverters, the methodcomprising: setting a selection signal to apply a second sub pulsesignal to at least one of the sub half-bridge inverters; transmittingpower to at least one coil cell by applying an enable signal to the atleast one sub half-bridge inverter; and when the at least one coil cellreceives a response from a wireless power receiver, changing theselection signal to apply a first sub pulse signal to the at least onesub half-bridge inverter, wherein the first sub pulse signal is aphase-inverted version of a main pulse signal applied to the mainhalf-bridge inverter and the second sub pulse signal is aphase-controlled version of the main pulse signal.
 9. The method ofclaim 8, further comprising, when the at least one coil cell receives noresponse from a wireless power receiver, terminating the application ofthe enable signal.
 10. The method of claim 8, further comprising, whenthe at least one coil cell receives a response from a wireless powerreceiver, determining whether the wireless power receiver isinductive-type or resonant-type.
 11. The method of claim 10, furthercomprising, when the wireless power receiver is inductive-type,controlling the phase of the second sub pulse signal, instead ofchanging the selection signal.
 12. The method of claim 8, wherein theresponse from the wireless power receiver comprises mode information,and the mode information indicates whether the wireless power receiveris inductive-type or resonant-type.
 13. The method of claim 8, whereinthe enable signal is applied to the at least one sub half-bridgeinverter, either simultaneously or sequentially.